Electromagnetic sound powered telephone



June 21, 1949. G. L. DIIMMICK 2,474,197

ELEC TROMAGN E T I G S OUND POWERED TELEPHONE Filed May 31, 1940 Patented June 21, 1949 UNITED? S O F ELECTROMAGNETIC SOUND POWERED A TELEPHONE GlenniLrDimmicln-Hadd Radio scorporationi i of of Delaware onfielcl'; N .J assignor 'to:

America; :a corporation s Application MaYSl, 1940, SriaI'NO. 338,057

5 CIaimSwtCI. 179---1'1-5 transducer adapted to act either particularly to a telephonic: as a' transmitter to generate electrical oscillationsinresponsetto acoustical energy, or

as a'receiver. to translate electrical oscillations into :acoustical vibrations;

The principal object. of my present invention ism to provide a' transducer as aforesaid .havingim-r. proved efliciency'and 'ru'ggedness over similar devices heretofore known: a

More particularly, invention to provide is extended over a Another obj ect' of my present invention is to it is an object of' my present an improved transducer as 1 aforesaid in which the high frequency'response wider range'th'an heretofore.

provide an improved transducer-assetforth above which will not be subject to damageupon' sudden and excessive changes in air pressure'in the vicinity of the diaphragmthereof.

A furtheriobject of my present invention is: to a provide an improved transducer of'the"type-set forth above which which readily lends facture;

In accordance with y present inventiomm 1 th 212mm or: less 'co'nvenr: v

vide the transducer tional electromagnetic:motor' ior generator, :as

is 'simplel intconstruc'tiona-and I itself-2 to economica1 manu-- the case maybe, andform'the couplingrod which couples. the armature of :the magnetic unit t'o .the I diaphragm with a 'complian'ceain the form :of' an elastic ilinkgi'This 'results'in a three'epeak system t instead "ofithe two-peaksystem-previously-known,

the third'peak extending .1;1'16 high frequency range considerably. Behind the diaphragmg an a annular backing plate maybe placed "to' protect the diaphragm from excessivezdeflection, ithe l space between the backing plate:

width of the air gap'ini whichtthe .arma-tun-i of the aforementioned unitoperat'es. :Also, apain- 'andil'diap'hragm being approximatelyi of the isameaorder' 'as the:

of spacing rings,'one in front'andthe other jush' behind the diaphragm, are provided to clampthe marginal portion of the diaphragmuto hold-itiim place. The spacing ring immedialtely behind the diaphragm is'preferably made widen to extend radially inwardly'of the diaphragm a greater distance than the front spacing TiIlgZ aHdthiS-EWGS added protection to the diaphragmegainst exces sive deflection. 2T0 further prevent *the ldia phragm from damageiby excessive deflectionand to provide acoustic protectiontherefor;I- p1ovide-' a flap valve which is" placed ad rise in pressure, such istic iof my invention larityr'in the appended claimsw 'lhe invention it self, showever, both as to its methodiof: operation, as

with the accompanying'drawing,in which 1' V :Figiire-is a view'partlyin sectionshowing unit formed in accordance with certain featt1res of my invention,

Figure'z-is a wiring diagram showing the cloc the mechanical-acoustical trical equivalent of systemofsFigure l,

FigUre 3-F-is' a response curve ofthe system shQWndn-Figure 1,

Figure 141's a view similar-toFigur'e 1 showing certainrother features ofimy invention, and

;; Figure fi is a fragmentary planview ofth'e device shown 'in'v Figure 4.

Referring'rmore particularly to the drawing; whereinaisimilar reference numerals designate correspondingi parts-throughout, I have shown;- in

Figurefzljl-an acoustic diaphragm' l clampedat its marginal iportionbetween a pair of clamping rings 3 and covered with a-cover 'plate' 5 having one'ormore: openings l-thereinp- Connected to the diaphragm l'at one-of its ends ture tl: of the cantilever type rigidly secured to nonmagnetic 7. insert between the pole-pieces l3; amagnet l7 supplyan Seshaped or accordion-like link mately 500 cycles as shown by the response curve of Figure 3wherein the dotted curve indicatesthe known two peak sys-' tems' and--thesolid line represents the response response -of the "previously of my improved"three-peak "system;

The fiect 'of' the elastic-link or compliance '19 will befidetterunderstoodby'reference to-Figure'2: If Lirepresents the efi'ectiVe mass ofthe 'air in" the opening- 7,-Ci represents the elastance ofthe organization and-=' welt-as additional--objects andiadvantagesthereof,'wi1l best be under stood from'ithe "following description of several embodimentsrthereof; .when read I in connection is a driverod 9 whiohihasiits other'end connected to an arma l2 betweena pairof pole' piece'sdfi: and extending through=an air gapl9r'which-con--- stitutesla' compliance which is symmetrical" with air in the cavity between the cover plate and the diaphragm I, L2 and C2 represent the mass and the elastance of the diaphragm 1, respectively, L3 and C3 represent, respectively, the mass and elastance of armature H, and C4 represents the elastance of the link 19, then the relation in the corresponding electrical circuit will be as shown in Figure 2. It is the introduction of the elastance or capacitance C4 in the system which results in the third peak shown at the extreme right in Figure 3.

Devices of the type herein described are used quite extensively on battleships for communication from one part of the ship to another. It frequently happens, upon the firing of a gun in the neighborhood of one of the units, that the sudden rise in pressure in front of the cover plate 5 resulting from the blast causes the diaphragm i to break as the result of excessive deflection.

To prevent this, I provide the structure shown in Figures 4 and 5. In this form of my invention, the diaphragm l is clamped between a pair of rings 2! and 23, the latter of which engages the rear surface of the diaphragm and is wider than the former, thereby extending radially inwardly a distance greater than the ring 25. Resting against the ring 2! is a cover plate which has a relatively thin, central region and a relatively thick, marginal portion 2?, the central region of the plate 25 being provided with a plurality of openings or perforations 29 corresponding to the opening i of Figure l. Clamped against the outer, marginal face of the cover plate 25 and spaced slightly from the central, perforated region thereof is a flap valve Ell which is provided with a plurality of perforations 3.3 staggered with respect to the perforations 2d, the valve member 31 being held against the plate ill by the inwardly extending flange 35 of a cap member 37 which is threaded onto a back plate 39. Also secured to the marginal portion 21 at the inner face thereof is a second flap valve 32 having a plurality of perforations 3 therein aligned with the perforations 33 and similarly staggered with respect to the perforations 29. The valve member 32 may be secured to the cover plate 25 by means of a clamping ring 38 and screws 38. Preferably, although not necessarily, the valves 3! and 32 may be made in the form of spiders having central circular portions and radially outwardly extending arms which are clamped against the cover plate, as clearly shown in Figure 5.

From the foregoing description, it will be obvious that, upon a sudden and excessive rise in air pressure in front of the cover plate 25 resulting, for example, from the blast of a gun, the outer valve 3| will be forced against the plate 25 to close the perforations or ports 25 therein through which normal acoustical air waves may pass freely to or from the diaphragm l. Similarly, if there is a sudden rarefaction of air in front of the cover plate 25 resulting in a sudden and excessive decrease in air pressure, the valve 32 will close against the ports or perforations 29 on the other side of the plate 25 and again prevent abnormal displacement of the diaphragm l, but this time in a forward direction. Since the diaphragm l is most apt to be unduly or excessively displaced in a rearward direction rather than a forward direction, additional precaution may be taken to safeguard the diaphragm by making the clamping ring 23 wider than the clamping ring 2| and by having the backing plate 39 extend radially inwardly of the diaphragm l a considerable distance, as clearly shown in Figure 4. The

- tion stiffness of the edge of the diaphragm l for very small vibrations is determined by the width of the narrower spacing ring 2|, but for large deflections toward the rear, the edge of the diaphragm is protected by the wider spacing ring 23. The backing plate 39 is sufficiently close to the fold to of the diaphragm I to form a support for the diaphragm after it has been deflected an amount slightly less than that permitted by the air gap 15. This greatly adds to the effective maximum strength of the diaphragm.

From the foregoing description, it will be apparent to those skilled in the art that I have provided an improved sound-powered telephone unit which is not only rugged in construction, but which is also responsive over a wider range than heretofore. The spiders or valves 3! and 32 are preferably made of thin metal. For any normal forces, such as those due to wind, the stiffness of the spiders is great enough to hold the central portions thereof away from the cover plate and to allow the voice or acoustical waves to act upon the diaphragm when the device is used as a transmitter, However, as noted heretofore, large forces, such as those due to gun fire, will cause one or the other of the spider flap valves to close against the cover plate and prevent damage to the diaphragm or other parts of the unit. After the blast of the gun fire is over, the unit is im mediately ready for use again.

Although I have shown and described several forms of my invention, it will be apparent to those skilled in the art that many variations thereof are possible. I, therefore, desire that my invenshall not be limited except insofar as is made necessary by the prior art and by the spirit of the appended claims.

I claim as my invention:

1. A telephonic transducer comprising a vibra tile member, an electromechanical unit including a movable element, and means coupling said movable element to said vibratile member, said means having an axis of motion and being movable freely along said axis, and said means having an accordion-like compliance therein symmetrical with respect to its said axis.

2. A telephonic transducer comprising a diaphragm, a reversible electromechanical unit including an armature, and means coupling said armature to said diaphragm, said means having an axis of motion and being movable freely along said axis, and said means having an S-shaped compliance therein symmetrical with respect to said axis.

3. A telephonic transducer comprising a diaphragm, a reversible electromechanical unit including an armature, and a driving rod connecting said armature to said diaphragm, said driving rod having an axis of motion and being movable freely along said axis, and said driving rod having an accordion-like link therein symmetrical with respect to said axis.

4. A telephonic transducer comprising a diaphragm, a reversible electromechanical unit including an armature, and a driving rod having one end connected to said diaphragm and its other end connected to said armature, said driving rod having an axis of motion and being movable freely along said axis, and said driving rod having an S-shaped link intermediate its ends which is symmetrical with respect to said axis.

5. A telephonic transducer comprising a vibratile member, an electromechanical unit including an armature, and means coupling said armature to said diaphragm, said coupling means having an axis of motion and being movable freely along said axis, and said coupling means extending generally in a direction normal to said. armature and including a portion which is compliant generally in said direction said compliant portion being symmetrical with respect to said axis.

GLENN L. DIMMICK.

REFERENCES CITED The following references are of record in the 10 file of this patent:

UNITED STATES PATENTS Number Name Date 711,640 Miner Oct. 21, 1902 1,341,154 Pepin May 25, 1920 Number Number 15 326,626 462,397

Great Britain Mar. 9, 1937 

